Moved from http client implementation to etcd-rb implementation.

We use the https://github.com/iconara/etcd-rb code; also, I added
a support for hashes and arrays in hiera fetching data stored in json
format in etcd.
Typos fixed
A few more changes and now everything works.

- Migrated to https://github.com/ranjib/etcd-ruby which has a nicer interface.
- small fixes
some more type checking
Better error handling.

Now errors are checked in place, and strict type checking is
enforced.
Merge pull request #1 from lavagetto/master

Use etcd-ruby for reqests instead of plain http.